Diptera: Chironomidae) in the Alaskan Arctic

CHIRONOMUS Journal of Chironomidae Research No. 33, 2020: 48-58. Current Research.

Evidence of parthenogenetic populations from the Paratanytarsus laccophilus species group (Diptera: Chironomidae) in the Alaskan Arctic

Alec R. Lackmann1,2, Daniel C. McEwen3, Malcolm G. Butler4

1University of Minnesota Duluth, Department of Biology, 1035 Kirby Drive, SSB 207, Duluth, MN 55812. 2North Dakota State University, Department of Biological Sciences, Environmental and Conservation Sci- ences Program, PO Box 6050, Fargo, North Dakota, USA 58108. E-mail: [email protected] 3Limnopro Aquatic Science, Inc. PO Box 764, St. Cloud, MN 56302. E-mail: [email protected] 4North Dakota State University, Department of Biological Sciences, Fargo, North Dakota, USA. E-mail: [email protected]

Abstract Introduction Parthenogenesis, reproduction without fertiliza- While sexual reproduction is widespread in the tion, is not common in the Chironomidae (Dip- animal kingdom, parthenogenesis is a widespread tera), a family of insects with more than 6,000 form of asexual reproduction in which there is no described species. Nonetheless, parthenogenetic fertilization of the egg (Suomalainen 1962; Lynch species and strains have been documented in at 1984). Parthenogenesis in animals evolves most least three subfamilies (the Chironominae, Or- commonly as an artifact of hybridization (Carew et thocladiinae, and Telmatogoninae), spanning 17 al. 2013) and is most often thelytokous, i.e. where genera and ~30 species. One such species, Para- all asexually produced offspring are female. Be- tanytarsus laccophilus Edwards 1929, is known to cause offspring are genetically monotonous with be parthenogenetic in a small portion of its range mutation as the only source of variation (Lynch in Finland, with most other European populations 1984), parthenogenesis is often considered an evo- of this species showing evidence of sexual repro- lutionary dead end (Darlington 1946; Mayr 1970; duction. We present evidence of parthenogenetic Smith 1978). Nonetheless, patterns exist in the populations from the Paratanytarsus laccophilus distribution of parthenogenetic forms that suggest species group in the Nearctic, specifically a High this reproductive strategy could be evolutionarily Arctic site near Utqiaġvik (formerly Barrow), advantageous in certain cases. Alaska. During May-July of 2015 and 2016, we “Geographic parthenogenesis” describes the ob- sampled emerging adult chironomids and pupal servation that parthenogenesis tends to evolve exuviae daily to document insect emergence phe- in habitats that are different from where their nologies. Across 15 local populations, all 623 pu- closely related, sexually-reproducing relatives re- pal exuviae collected from the P. laccophilus spe- side (Vandel 1928). Indeed, parthenogenetic species group were female. Larvae reared from two cies are most commonly documented from high populations under controlled temperature treat- latitudes, especially in harsh habitat conditions ments emerged as female adults (N=37). When (Lynch 1984). Proposals articulated to account for isolated, these reared female adults oviposited, and this phenomenon include the “biotic-uncertain- eggs hatched successfully. These progeny were ty” hypothesis (Ghiselin 1974), and the “tangled reared for another 12-13 days, reaching second bank” hypothesis (Bell 1982). The biotic-uncer- instar larvae when they were preserved at the end tainty hypothesis postulates that parthenogens tend of our field season. Taken together, this evidence to persist in harsh environments that are relatively strongly indicates parthenogenesis from the P. lac- barren biologically, and an environment with mini- cophilus species group at this location. This spe- mal biotic interaction favors the persistence of ge- cies was not previously documented at Utqiaġvik. netically monotonous lineages. The tangled bank Although parthenogenetic, their emergence at this hypothesis argues that harsh environments are location was highly synchronized. In the harsh en- less niche-specialized because they are frequently vironment of arctic Alaska, the fitness rewards of disturbed. This selects against genetically diverse parthenogenesis are likely great. Indeed, chirono- progeny pre-adapted to fill a diverse array of nich- mid parthenogenesis in the northern hemisphere es, providing opportunities for clonal populations. is most commonly documented from far-northern These rather intuitive hypotheses include many as- extremes and in extreme habitats. sumptions, remain untested, and are unsatisfactory in explaining geographic parthenogenesis (Lynch 1984).

48 Although parthenogenesis is rather widespread Of the at least 6,434 described chironomid spe- across some insect groups such as the Hymenop- cies to date (ISC 2017; Stur and Ekrem 2020), less tera (Suomalainen 1962), it is relatively uncom- than 0.5% (~30 species) are known as partheno- mon in the Chironomidae (Lindeberg 1951; Armit- gens (Table 1). These represent 3 of the 11 extant age et al. 1995; Gokhman and Kuznetsova 2017). chironomid subfamilies (Cranston et al. 2012): the These non-biting midge flies are often the most Chironominae, Orthocladiinae, and Telmatogoni- common and species-rich macroinvertebrate taxon nae. In the Chironominae, there are 17 partheno- in freshwater habitats, with estimates of the total genetic species found among 7 genera (Grimm richness of this family surpassing 10,000 species 1870; Thienemann 1954; Lindeberg 1958; Linde- (Armitage et al. 1995), with the tropics still poorly berg 1971; Grodhaus 1971; Oliver and Danks studied (Ferrington 2007). 1972; Armitage et al. 1995; Langton 1998; Donato and Paggi 2008; Porter and Martin 2011); in the

Table 1. Chironomid taxa with evidence of parthenogenesis as of 2020.

Subfamily Taxon Reference Chironominae Tanytarsus norvegicus (Kieffer, 1924) Lindeberg 1971 Tanytarsus gregarius (Kieffer, 1909) Lindeberg 1971 Tanytarsus sp. (sylvaticus) Lindeberg 1971 Tanytarsus sp. (lestagei) Lindeberg 1971 Tanytarsus heliomesonyctios (Langton, 1999) Langton 1998 Paratanytarsus grimmii (Schneider, 1885) Grimm 1870 Paratanytarsus laccophilus (Edwards, 1929) Lindeberg 1958 Paratanytarsus sp. (boiemicus) Lindeberg 1971 Micropsectra silvesterae (Langton, 1999) Langton 1998 Micropsectra sp. (nigripila) Armitage et al. 1995 Micropsectra sedna (Oliver, 1976) Porter et al. 2011 Chironomus atrella (Townes, 1945) Grodhaus 1971 Chironomus attenuatus (Walker, 1848) Grodhaus 1971 Chironomus stigmaterus (Say, 1823) Grodhaus 1971 Lauterborniella sp. Oliver et al. 1972 Polypedilum parthenogeneticum (Donato and Paggi, 2008) Donato et al. 2008 Zavreliella marmorata (Wulp, 1858) Thienemann 1954 Orthocladiinae Corynoneura celeripes (Winnertz, 1852) Edwards 1919 Corynoneura donovani (Forsyth, 1971) Forsyth 1971 Corynoneura scutellata (Winnertz, 1846) Edward et al. 1968 Limnophyes minimus (Meigen, 1818) Armitage et al. 1995 Limnophyes vestitus (Skuse, 1889) Forsyth 1971 Abiskomyia virgo (Edwards, 1937) Armitage et al. 1995 Bryophaenocladius furcatus (Kieffer, 1916) Armitage et al. 1995 Eretmoptera murphyi (Schaeffer, 1914) Armitage et al. 1995 Metriocnemus abdominoflavatus (Picado, 1913) Thienemann 1954 Phytotelmatocladius delarosai (Epler, 2010) Siri et al. 2014 Pseudosmittia baueri (Strenzke, 1960) Armitage et al. 1995 Troglocladius hajdi (Andersen, Baranov et Hagenlund, 2016) Andersen et al. 2016 Telmatogetoninae Telmatogeton amphibious (Eaton, 1875) Crafford 1971 Telmatogeton sp. Delettre et al. 2003

49 Orthocladiinae there are 12 species from 9 genera identifying female midges, parthenogenesis in the (Edwards 1919; Thienemann 1954; Edward and Chironomidae may be more common than previ- Colless 1968; Forsyth 1971; Armitage et al. 1995; ously believed (Ekrem et al. 2010; Stur and Ekrem Siri and Donato 2014; Andersen et al. 2016; Bart- 2020). lett et al. 2018); and in the Telmatogetoninae there Not only do parthenogenetic chironomids vary in are two species from the type genus Telmatogeton habitat, but they also vary in the extent of their (Crafford 1971; Delettre et al. 2003). parthenogenesis. Some of the taxa in Table 1 are Of all these parthenogenetic species (Table 1), strictly parthenogenetic, like Paratanytarsus grim- the best represented genera are Tanytarsus, Para- mii, the globally-distributed, notorious pest of tanytarsus, Micropsectra, Corynoneura, and Lim- water-supply systems (Carew et al. 2013). Other nophyes, while at the other extreme some genera taxa (e.g. Tanytarsus heliomesonyctios) exhibit show very limited evidence of parthenogenesis population-specific parthenogenesis, with parthe- (e.g. Chironomus) (Oliver and Danks 1972; Armit- nogenesis evident for populations that occur in age et al. 1995). Although most parthenogenetic relatively harsh environmental conditions (Orel chironomids are found in arctic and subarctic and Semenchenko 2019; Stur and Ekrem 2020). habitats (Armitage et al. 1995), others are reported This is also the case for Paratanytarsus laccophi- from sub-Antarctic islands (Crafford 1971; Delet- lus. Lindeberg (1958, 1971) documented parthe- tre et al. 2003), phytotelmata in Argentina (Siri et nogenetic populations of P. laccophilus in rock al. 2014), and a cave in Croatia (Andersen et al. pools on the isles of the Gulf of Finland, yet found 2016). Furthermore, since many of these parthe- bisexual reproduction in all other locations where nogenetic chironomids are triploid and of hybrid he studied this species. Here we present evidence origin, they are permanent genetic heterozygotes of additional parthenogenetic populations from the that may be more apt to find certain habitats suit- P. laccophilus species group, found in the North able (Carew et al. 2013). Considering the wide American High Arctic near Utqiaġvik, Alaska. range of habitats and the taxonomic difficulty of

Figure 1. Map of the field site at Utqiaġvik, Alaska. Individuals of the Paratanytarsus laccophilus species group were taken from the fifteen tundra ponds labeled (red dots). Scale bars = 500 km (inset), and 1 km.

50 Materials and Methods perature (±1°C) with EcoPlus™ aquarium chillers and monitored with Onset® Hoboware tempera- The study site is located at Utqiaġvik (formerly ture loggers. We monitored larvae and pupae daily Barrow), Alaska (71°17’27.5”N 156°47’18.5”W). for development and emergence of adult flies. For We sampled a total of fourteen tundra ponds (Fig. each emerged specimen, we recorded temperature 1) within an 8 km radius of the village for chi- treatment, source pond, species, sex (confirmed ronomid pupal exuviae (PEs) across the 2015 and by examination of PE genital structures under a 2016 emergence seasons (i.e. from thaw in mid- dissecting microscope), and date of eclosion. We late May to late July, when chironomid emergence immediately preserved emerged adults and their ended). We conducted this phenological sampling pupal exuviae (PEs) in 70% EtOH, except when daily in both years, with Ponds A, C, E, J, G, and an emerged singleton from the P. laccophilus spe- Kaleak sampled on even days, while Ponds Bear, cies group was confirmed (see below). Adults were OH, HB, Icy, and Sub-Bear sampled on odd days. photographed laterally under a Wild dissecting Ponds Snowfence and Scuzzy were part of the odd microscope (Fig. 2) in a thin film of 70% EtOH day sampling in 2015 only, and Pond Infinity was - just enough to submerse the specimen such that sampled only twice in 2015. individuals would lie laterally. Photomicroscopy Ponds A, C, E, J, G, OH, Bear, and Infinity are was done with a Canon EOS Rebel T3i camera at- low-centered polygon ponds (Liljedahl et al. 2012) tached to a trinocular mount. with a maximum depth of 0.5 m, surface areas largely consisting of open water, and ranging in We isolated reared singletons of the P. laccophilus size from ~175 m2 to 900 m2 total area. Ponds HB species group that were confirmed as virgin (i.e. and Icy are degrading ice-wedge ponds (Liljedahl no other species or conspecifics had emerged in et al. 2012) with a maximum depth of 2 m, largely that daily cohort) by first locating the adult midge open water, and size ranging from ~120 m2 to 180 beneath the mesh of the rearing cup by shining a m2 total area. Ponds Kaleak, Snowfence, Sub-Bear, light through the base of the cup (Fig. 3a). When and Scuzzy are the smallest ponds (areas ~18 m2 to a potential specimen was located, we carefully 750 m2) and shallowest (maximum depth ~30 cm) coaxed her to the mesh of the lid (were she not and are thoroughly vegetated with Carex and Arc- already there). As adults of this species are fast tophila. Sub-Bear, and Scuzzy are so shallow they and agile fliers, we took care to prevent escapees. Once the female was on the mesh, (Fig. 3a), we lost most standing water by late June). carefully unscrewed the lid and quickly placed it Samples consisted of five 1 m dip net sweeps on the table, trapping the fly. We then located and taken on the downwind side of the pond to collect identified the lone PE within the opened rearing surface-floating PEs and emerging or failed adults. cup to confirm it was of the P. laccophilus spe- Pooled net contents were stored in 35% ethanol cies group (Fig. 3b). If confirmed, we prepared a in the field, and subsequently transferred to 70% new rearing cup containing only pond water. The ethanol. Sampled PEs were sorted, sexed, and tal- lid with the trapped female clinging to the mesh lied in the lab under a dissecting microscope, and was then quickly transferred to the new rearing identified to species group according to - Wieder cup. We monitored these isolated individuals for holm (1986). behavior, and ultimately, oviposition. If oviposi- While processing 2015 field samples, it became tion took place, we monitored and photographed evident that individuals of the P. laccophilus spe- the egg mass daily under a dissecting microscope, cies group might be parthenogenetic due to a lack watching for egg development and hatching. Once of males. In 2016 we took larval samples for rear- hatched and larvulae had consumed the gelatinous ing under controlled temperature conditions in the mass surrounding the eggs, we added filtered (50 lab. These larvae came from Kaleak Pond on 19 μm) pond detritus (free of exotic chironomid lar- and 28 June, and from Pond T-BARC (Fig. 1) on vae) to each microcosm. 30 June. Small tanytarsine larvae hypothesized to We used JMP 14 Pro Statistical Discovery™ for include individuals of the P. laccophilus species statistical analysis and graphical output. Degree group were batch-placed into rearing cups (repli- hours (DH) for each emerged specimen were cal- cated thrice) with detritus and pond water and incu- culated as mean temperature experienced*total bated at eight temperature treatments ranging from hours for development. 5-25 °C (as this rearing setup was part of another study testing chironomid developmental responses Results to temperature). These lab incubations consisted of Over the 2015 and 2016 field seasons, we collect- eight oxygenated aquaria controlled for water tem- ed a total of 623 PEs of the P. laccophilus species

51 Figure 2. Lateral view of a recently emerged individual (female) of the Paratanytarsus laccophilus species group in Utqiaġvik, Alaska. The specimen was submerged in a thin film of 70% EtOH immediately after it emerged from a rearing cup in the lab, and her natural coloration was captured via photomicroscopy. Scale bar = 1 mm.

Figure 3. a) A freshly emerged, virgin individual of the Paratanytarsus laccophilus species group (arrow) clinging to the mesh lid of the new rearing cup to which it was transferred. The isolated female was then monitored daily for signs of oviposition. b) The pupal exuviae (PE) collected from the larval rearing cup, used to confirm species-group identification. Note the diagnostic patterning on abdominal tergites III and IV (Wiederholm 1986). Scale bar in (b) = 0.5 mm.

52 group, identified according to Wiederholm (1986). In 2015 and 2016 the median date of emergence All specimens were female, and came from four- was also the date of peak emergence in both years teen tundra ponds (Fig. 1) representing a range of (Julian dates 170 and 190 respectively). habitat types (see methods). We also reared 37 in- Despite this synchrony, this species’ emergence dividuals of the P. laccophilus species group (all timing varied across years. Thaw dates were nearly female), from larvae, collected from two pond identical in Kaleak Pond between 2015 and 2016, sources, to emergence under lab conditions (Table with only a two-day difference - 2015 having the 2). later start (Fig. 4b). Yet peak emergence of this Kaleak Pond produced the most specimens of the species in 2015 was ~20 days earlier than in 2016 P. laccophilus species group of all habitats across (Fig. 4a). This difference in phenological emer- both years, and the PE sweep data from this pond of- gence pulse corresponds to a difference of more fers insight into the species’ emergence phenology than 3,800 DH between the two years. In 2015, (Fig. 4). This species showed highly synchronized the median degree hour experience from thaw to emergence, even compared to other, sexually-re- emergence was 4,102 (mean: 5,339 ± 378 [95% producing species at Utqiaġvik (Butler 1980a). In CI]), while in 2016 it was 7,986 (mean: 8,026 ± 2015, the peak emergence date (the date on which 132 [95% CI]). Comparing median values, the DH the greatest number of this species emerged for a experienced from thaw to emergence in 2015 was given year) for individuals of the P. laccophilus just 51% of that experienced in 2016. species group (Julian date 170) was also the first day PEs of this species were collected from this Of the 37 individual larvae reared adults (all were pond, and these comprised 76% (139/183) of that female) in the lab, three emerged as singletons. season’s total. Our 2015 sampling in Kaleak be- These were transferred into their own rearing cups gan 20 days earlier (on Julian date 150: 30 May), and tracked for behavior and oviposition. These and no PEs of this species were collected on any adult females were most often seen clinging to the of the 13 day-specific samples prior to peak emer- mesh lid (Fig. 3a), but were sometimes observed gence on Julian date 170 (19 June). In 2016, 72% skittering across, or resting on the water’s surface (242/338) of all collected individuals of this spe- in the rearing cup. We found one adult “belly-up” cies emerged in three consecutive samples from on the surface of the water three days after she 4-8 July (Julian dates 186, 188, and 190), with the eclosed and was moved to her isolated cup (Table peak for this year being 8 July (Fig. 4a), again doc- 3). The adult was confirmed dead, and no signs of umenting a high degree of emergence synchrony. progeny were discovered in the rearing cup (e.g. no egg mass or larvae). Table 2. Collection information for individuals of the Paratanytarsus laccophilus species group in the present study.

N (2015, 2016) N (total) % ♀ Pond Coordinates Sample type (183, 338) 521 100 Kaleak 71°17’54.36”N, 156°41’46.32”W PE sweep (36, NA) 36 100 Snowfence 71°17’23.52”N, 156°39’45.09”W PE sweep (1, 12) 13 100 Icy 71°16’39.46”N, 156°38’31.29”W PE sweep (4, 3) 7 100 J 71°17’36.75”N, 156°42’5.43”W PE sweep (2, 5) 7 100 G 71°17’32.84”N, 156°42’3.55”W PE sweep (2, 4) 6 100 Sub-bear 71°16’36.36”N, 156°38’24.19”W PE sweep (3, 2) 5 100 A 71°17’41.33”N, 156°42’9.39”W PE sweep (1, 4) 5 100 HB 71°16’38.42”N, 156°38’32.46”W PE sweep (5, NA) 5 100 Scuzzy 71°16’38.72”N, 156°38’31.49”W PE sweep (0, 5) 5 100 Bear 71°16’37.11”N, 156°38’22.99”W PE sweep (4, NA) 4 100 Infinity 71°17’4.26”N, 156°34’22.65”W PE sweep (1, 2) 3 100 C 71°17’40.21”N, 156°42’8.06”W PE sweep (1, 2) 3 100 E 71°17’38.85”N, 156°42’6.81”W PE sweep (1, 2) 3 100 OH 71°16’35.25”N, 156°38’27.91”W PE sweep (NA, 34) 34 100 Kaleak 71°17’54.36”N, 156°41’46.32”W Lab rearing (NA, 3) 3 100 T-BARC 71°19’25.18”N, 156°40’7.30”W Lab rearing N(All) 660 100 15 NA

53 Figure 4. a) Emergence synchrony of individuals of the Paratanytarsus laccophilus species group as evidenced by pupal exuviae count vs. sample date (Julian) in 2015 and 2016 from Kaleak Pond. In both years sampling began on Julian day 150 (30 May and 29 May, respectively). In 2015 sampling concluded on Julian date 201 (20 July), and in 2016 on day 213 (31 July). b) Hourly temperature (°C) vs. Julian date from a Hoboware data logger in Kaleak Pond. Thaw was defined according to McEwen and Butler (2018) using the pond-specific logger. In 2015 pond thaw occurred on day 139 (19 May), and in 2016 on day 137 (16 May). The red curve through the data points represents the cubic spline with a bootstrap confidence region at lambda = 0.05.

The other adults died 2-3 days after eclosion. Upon After we added pond detritus to the rearing cups, inspection, a single egg mass was immediately the newly hatched larvulae grew and developed noticeable in the bottom of each cup (Fig. 5a-b). in their respective temperature treatments for the These egg masses consisted of a string of eggs in remaining duration of the field season. As this spe- a spiral, within an outer, oval-shaped, gelatinous cies emerged rather late in the season (Fig. 4a) mass. After 2-5 days (depending on treatment) the compared to known chironomid phenologies at eggs hatched (Fig. 5c-g). Larvulae remained within Utqiaġvik (Butler 1980a; Butler 1982; Braegel- the spiral of the egg rope (e.g. Fig. 5g) in the hours man 2016; Lackmann and Butler 2018; Butler and immediately after hatch. By the next day they were Braegelman 2018), there was little time for addi- moving within the outer gelatinous matrix of the tional larval development as our field season ended egg mass or freely moving about the rearing cup. on 31 July. We preserved the thriving larvae on 28 The egg mass morphology, time between eclosion July and found numerous larval exuviae (LEs) in and deposition of the egg mass, egg number, time each rearing cup, indicating that these parthenoge- to hatch, and larvulae behavior are all concordant netically-produced larvae had molted to the sec- with Lindeberg’s (1958) pioneering work describ- ond larval instar. ing parthenogenetic populations of P. laccophilus in southern Finland. Table 3. Individual adults from the Paratanytarsus laccophilus species group reared in isolation and their subsequent life history events. All three individuals came from Kaleak Pond. Individual (I); Temperature treatment (Trt); Larval exuviae (LEs)

I Trt. (°C) Eclosion Oviposit Adult perished # of eggs Hatch LEs present 1 18.3 2 July NA 5 July NA NA NA 2 15.3 8 July 11 July 11 July 109 16 July 28 July 3 21.0 11 July 13 July 13 July 87 15 July 28 July

54 Discussion In cases like Paratanytarsus laccophilus, where parthenogenesis appears population-specific, it remains unclear if populations are facultatively parthenogenetic in certain environments, or if ob- ligatory bisexual and asexual strains have evolved independently and now coexist globally (Linde- berg 1971; Oliver and Danks 1972; Armitage et al. 1995). No matter how it evolved, parthenogenesis in a chironomid at Utqiaġvik, AK should not be surprising. The study site is located in the High Arctic where temperatures are low, winds are high, and the overwintering period encompasses most of the year (Butler 1980a). The fitness benefits of being parthenogenetic in such a habitat are likely great because every individual in the population is female and is theoretically capable of producing offspring herself. The risk involved in finding a mate is avoided, and only one individual is hypo- thetically necessary to establish a population in a new habitat (Lynch 1984). This allows for rapid population growth and productivity. Sexually reproducing species tend to require more individuals for population establishment to be successful, because future generations may be unlikely to find mates if founding numbers are low (Suomalainen 1962; Lynch 1984; Bartlett et al. 2018; 2020). It is unknown when individuals of the Para- tanytarsus laccophilus species group colonized Utqiaġvik. Similar to what has been completed for Paratanytarsus grimmii (Carew et al. 2013), genetic analyses on populations of P. laccophilus at a global scale (e.g. from Finland and Alaska) would be valuable in understanding this history, and in determining the exact taxonomic position of these Alaskan populations. Such genetic information could provide insight on the dispersal of P. laccophilus over evolutionary time and provide a basis for interpreting the species’ present trajectory. It is interesting to note that this species group was not Figure 5. Development of parthenogenetic Paratanytarsus documented in the Utqiaġvik chironomid fauna laccophilus species-group progeny in the 15.3 °C treatment during the 1970s (Lougheed et al. 2011), and that in 2016. a) An egg mass freshly laid on 11 July. b) The same the habitats where this species was most abundant egg mass on 15 July, just before hatch. c-g) Daily progres- in the present study (thoroughly-vegetated, shal- sion of development. c) Eggs on 12 July 2016 at one day low tundra ponds) have also increased substan- old. d) At two days old. e) At three days old, eye spots (arrow) and head capsules were evident inside the egg. f) At tially over this timeframe (Liljedahl et al. 2016). four days old, eye spots and head capsules (arrow) were The species may simply have gone undetected dur- well-defined within the egg. g) Larvulae (arrow) hatched ing the 1970s because their habitat type was not on 16 July, five days after oviposition. Several vacated eggs as frequently sampled as it was in the 2010s. It is are clearly notable. Scale bar = 1 mm for a and b, and 250 also possible that this parthenogenetic species is μm for c-g. a recent invader of this polar extreme, similar to the parthenogenetic chironomid Eretmoptera murphyi that recently invaded Antarctica (Bartlett et al. 2018; 2020), but this remains unknown.

55 The highly synchronous emergence of this Alas- Acknowledgements kan population is intriguing considering males are This work was completed at North Dakota State lacking and females reproduce parthenogenetical- University (NDSU), USA as part of a doctoral dis- ly. Thus, selection for synchronized emergence for sertation by ARL. The North Slope Borough and the purpose of mate-finding, as proposed by Butler the Ukpeagvik Inupiat Corporation permitted ac- (1980a), would seem unnecessary. Perhaps their cess to the field site. We thank Ewelina Bielak- synchronized emergence is a heritage trait from Lackmann and Kevin Cortes for assistance in the sexually reproducing ancestors. Still, other fac- field and lab, and Dr. Shane D. Braegelman for tors (e.g. optimal temperatures and polarized light) helpful discussion and advice. We gratefully ac- might maintain such eclosion synchrony, even as knowledge financial support from the U.S. Arctic there is continuous light during the arctic growing Landscape Conservation Cooperative, the U.S. season, but this remains to be studied. In contrast, National Fish and Wildlife Foundation, and the the parthenogenetic and brachypterous E. murhpyi Environmental and Conservation Sciences Pro- that has invaded Antarctica ecloses asynchronous- ly across a broad phenology (2-3 months) (Bartlett gram at NDSU. et al. 2018; 2020). References Even though individuals of the P. laccophilus spe- Andersen, T., Baranov, V., Hagenlund, L.K., cies group emerged highly synchronously (i.e. Ivković, M., Kvifte, G.M., and Pavlek, M. >70% of total emergence occurred within a 4-day 2016. Blind flight? A new troglobiotic Ortho- interval in both years), their seasonal timing and clad (Diptera, Chironomidae) from the Lukina total heat sum from spring thaw to eclosion dif- Jama–Trojama Cave in Croatia. - PloS One fered substantially (Fig. 4). This may suggest that 11(4): e0152884. DOI: https://doi.org/10.1371/ larvae overwinter at different stages of develop- journal.pone.0152884 ment on a year-to-year basis depending on how much they can develop prior to the fall freeze, or Armitage, P.D., Cranston, P.S. and Pinder, L.C.V. that other environmental variables, that have so 1995. The Chironomidae. The biology and far gone unstudied, are significant drivers of their ecology of non-biting midges. Chapman & emergence timing. In the current climate change Hall, 572 p. era, arctic warming is amplified (IPCC 2014). If Baek, M.J., Yoon, T.J., and Bae, Y.J. 2012. De- individuals of the P. laccophilus species group velopment of Glyptotendipes tokunagai (Dip- colonized the Alaskan Arctic with the past 50 tera: Chironomidae) under different tempera- years, perhaps they are pre-adapted for this rapidly ture conditions. - Environmental Entomology evolving tundra landscape. Migratory shorebirds 41(4): 950-958. DOI: https://doi.org/10.1603/ are also well-documented to feed on chironomids EN11286 at this location (Braegelman 2016). If these popu- Bartlett, J.C., Convey, P., and Hayward, S.A. 2018. lations thrive under such a warming climate and Life cycle and phenology of an Antarctic in- evolving landscape, it might benefit some avian vader: the flightless chironomid midge, Eretm- insectivores. optera murphyi. - Polar Biology 42:1-16. DOI: Conclusion https://doi.org/10.1007/s00300-018-2403-5 We present evidence of parthenogenesis in an Bartlett, J.C., Convey, P., and Hayward, S.A. 2020. arctic Alaskan chironomid of the Paratanytarsus Surviving the Antarctic winter – Life stage laccophilus species group. This evidence suggests cold tolerance and ice entrapment survival in a reevaluation of geographic parthenogenesis in the invasive chironomid midge Eretmoptera P. laccophilus is necessary. It may turn out that murphyi. - Insects 11(3): 147. DOI: https://doi. Lindeberg’s original hypothesis of geographic org/10.3390/insects11030147 parthenogenesis in this species is correct (1958), Bell, G. 1982. The Masterpiece of Nature: The even though he later discarded it (1971). Although Evolution and Genetics of Sexuality. Univ. Ca- parthenogenesis in the Chironomidae is gener- lif. Press, Berkeley, 638 p. ally considered uncommon (Armitage et al. 1995), population-specific incidences such as P. lacco- Braegelman, S.D., 2016. Seasonality of some arc- philus suggest other sexually reproducing species tic Alaskan chironomids. Ph.D. Thesis, North may have parthenogenetic strains that are not yet Dakota State University, Fargo, North Dakota. known. 80p. Butler, M.G. 1980. Emergence phenologies of

56 some arctic Alaskan Chironomidae. In Murray, netic Chironomidae. - Journal of Natural D.A. (Ed.) Chironomidae Ecology, Systematics History 3(14), 222-228. DOI: https://doi. Cytology and Physiology, 1st Ed. Elsevier Ltd., org/10.1080/00222931908673815 pp. 307-314. Ekrem, T., Stur, E. and Hebert, P.D.N. 2010. Fe- Butler, M.G. 1982. A 7-year life cycle for two males do count: Documenting Chironomi- Chironomus species in arctic Alaskan tundra dae (Diptera) species diversity using DNA ponds (Diptera: Chironomidae). - Canadian barcoding. - Organisms Diversity & Evolu- Journal of Zoology 60(1): 58-70. DOI: https:// tion 10, 397–408. DOI: https://doi.org/10.1007/ doi.org/10.1139/z82-008 s13127-010-0034-y Butler, M.G., and Braegelman, S. D. 2018. Pre- Ferrington, L.C. 2007. Global diversity of non-bit- emergence growth and development in the ing midges (Chironomidae; Insecta-Diptera) in arctic midge Trichotanypus alaskensis Brun- freshwater. - Hydrobiologia 595, 447 (2008). din. - Journal of Limnology. DOI: https://doi. DOI: https://doi.org/10.1007/s10750-007- org/10.4081/jlimnol.2018.1836 9130-1 Carew, M., Gagliardi, B., and Hoffmann, A.A. Forsyth, D.J. 1971. Some New Zealand Chirono- 2013. Mitochondrial DNA suggests a single midae (Diptera). - Journal of the Royal Society maternal origin for the widespread triploid of New Zealand 1(2), 113-144. DOI: https:// parthenogenetic pest species, Paratanytarsus doi.org/10.1080/03036758.1971.10419345 grimmii, but microsatellite variation shows Ghiselin, M.T. 1974. The Economy of Nature and local endemism. - Insect Science 20(3), 345- the Evolution of Sex. Univ. Calif. Press, Berke- 357. DOI: https://doi.org/10.1111/j.1744- ley, 346 p. 7917.2012.01564.x Gokhman, V.E., and Kuznetsova, V.G. 2017. Par- Crafford, J.E. 1971. A case study of an alien in- thenogenesis in Hexapoda: holometabolous in- vertebrate (Limnophyes pusillus, Diptera, Chi- sects. - Journal of Zoological Systematics and ronomidae) introduced on Marion Island: se- Evolutionary Research, 56(1), 23-34. DOI: lective advantages. - South African Journal of https://doi.org/10.1111/jzs.12183 Antarctic Research Vol 4. Grimm, O.von. 1870. Die ungeschlechtliche Fort- Cranston, P.S., Hardy, N.B., and Morse, G. E. pflanzung einer Chironomus-Art und deren 2012. A dated molecular phylogeny for the Entwicklung aus dem unbefruchteten Ei. Zap. Chironomidae (Diptera). - Systematic En- imp. Akad, Nauk. 7: Serie 15: 1-24. tomology 37(1), 172-188. DOI: https://doi. org/10.1111/j.1365-3113.2011.00603.x Grodhaus, G. 1971. Sporadic parthenogenesis in three species of Chironomus (Diptera). - The Darlington, C.D. (1946). Evolution of genetic sys- Canadian Entomologist 103(3), 338-340. DOI: tems. Cambridge University Press: London. https://doi.org/10.4039/Ent103338-3 Delettre, Y.R., Frenot, Y., Vernon, P., and Chown, Intergovernmental Panel on Climate Change S.L. 2003. First record of Telmatogeton sp. (IPCC). Fifth Assessment Report 2014. (Diptera: Chironomidae) at Heard Island. - Po- lar Biology 26(6), 423-426. DOI: https://doi. International Symposium on Chironomidae (ISC) org/10.1007/s00300-003-0502-3 2017. Trento, Italy. Donato, M., and Paggi, A.C. 2008. Polypedilum Lackmann, A.R., and Butler, M.G. 2018. Breaking parthenogeneticum (Diptera: Chironomidae): the rule: Five larval instars in the podonomine a new parthenogenetic species from Eryn- midge Trichotanypus alaskensis Brundin gium L. (Apiaceae) phytotelmata. - Aquat- from Barrow, Alaska. - Journal of Limnology ic Insects 30(1), 51-60. DOI: https://doi. 77(s1), 31-39. DOI: https://doi.org/10.4081/ org/10.1080/01650420701829633 jlimnol.2018.1758 Edward, D.H., and Colless, D.H. 1968. Some Langton, P.H. 1998. Micropsectra silvesterae n. Australian parthenogenetic Chironomi- sp. and Tanytarsus heliomesonyctios n. sp. dae (Diptera). - Australian Journal of En- (Diptera: Chironomidae), two parthenogenetic tomology 7(2), 158-162. DOI: https://doi. species from Ellesmere Island, Arctic Canada. org/10.1111/j.1440-6055.1968.tb00724.x - Journal of the Kansas Entomological Society 208-215. Edwards, F.W. 1919. XX. Some parthenoge-

57 Liljedahl, A.K., Hinzman, L.D., and Schulla, J. Orel, O.V., and Semenchenko, A.A. 2019. Morpho- 2012. Ice-wedge polygon type controls low- logical description and DNA barcodes of adult gradient watershed-scale hydrology. In Pro- males of Tanytarsus heliomesonyctios Lang- ceedings of the Tenth International Conference ton, 1999 (Diptera, Chironomidae) in northeast on Permafrost Vol 1, 231-236. The Northern of Russia. - Zootaxa, 4686(1), 119-126. DOI: Publisher: Salekhard, Russia. https://doi.org/10.11646/zootaxa.4686.1.6 Liljedahl, A.K., Boike, J., Daanen, R.P., Fedorov, Porter, D.L., and Martin, J. 2011. Cytogenetics of A.N., Frost, G.V., Grosse, G., Hinzman, L.D., a parthenogenetic Arctic species of Micropsec- Iijma, Y., Jorgenson, J.C., Matveyeva, N., Nec- tra (Diptera, Chironomidae). - Comparative soiu, M., Raynolds, M.K., Romanovsky, V.E., Cytogenetics 5(4), 315-328. DOI: https://doi. Schulla, J., Tape, K.D., Walker, D.A., Wilson, org/10.3897/CompCytogen.v5i4.1356 C.J., Yabuki H., and Zona, D., 2016. Pan-Arctic Siri, A., and Donato, M. 2014. Monopelopia ice-wedge degradation in warming permafrost caraguata (Chironomidae: Tanypodinae: and its influence on tundra hydrology. -Nature Pentaneurini) and Phytotelmatocladius de- Geoscience, 9(4), 312-318. DOI: https://doi. larosai (Chironomidae: Orthocladiinae): org/10.1038/ngeo2674 two phytotelmatous chironomids distributed Lindeberg, B. 1958. A parthenogenetic race of from Florida to Argentina. - Florida Ento- Monotanytarsus boreoalpinus Th. (Dipt., Chi- mologist 97(3), 1226-1231. DOI: https://doi. ronomidae) from Finland. - Ann. Entomol. org/10.1653/024.097.0330 Fennici 24, 35-38. Smith, J.M. 1978. The evolution of sex (No. 574.1 Lindeberg, B. 1971. Parthenogenetic strains and S5). Cambridge: Cambridge University Press, unbalanced sex ratios in Tanytarsini (Diptera, 236 p. Chironomidae). - Annales Zoologici Fennici Stur, E., and Ekrem, T. 2020. The Chironomidae 310-317. (Diptera) of Svalbard and Jan Mayen. - In- Lougheed, V.L., Butler, M.G., McEwen, D.C., and sects, 11(3), 183. DOI: https://doi.org/10.3390/ Hobbie, J.E. 2011. Changes in tundra pond insects11030183 limnology: Re-sampling Alaskan ponds after Suomalainen, E. 1962. Significance of -par 40 years. - Ambio 40(6), 589-599. DOI: https:// thenogenesis in the evolution of insects. doi.org/10.1007/s13280-011-0165-1 - Annual Review of Entomology 7(1), 349- Lynch, M. 1984. Destabilizing hybridization, 366. DOI: https://doi.org/10.1146/annurev. general-purpose genotypes and geographic en.07.010162.002025 parthenogenesis. - The Quarterly Review of Thienemann, A. 1954. Chironomus. Leben, Ver- Biology, 59(3), 257-290. DOI: https://doi. breitung und Wirtschaftliche Bedeutung der org/10.1086/413902 Chironomiden. Binnengewiisser 20: 1-834. Mayr, E. 1970. Populations, Species, and Evolu- Vandel, A. 1928. La parthénogenèse géographique. tion. Belknap Press, Cambridge. Contribution à l’étude biologique et cy- McEwen, D.C., and Butler, M.G. 2018. Growing- tologique de la parthénogenèse naturelle. - Season Temperature Change across Four Dec- Bull. Biol. France Belg. 62, 164-281. ades in an Arctic Tundra Pond. - Arctic 71(3), Wiederholm, T. 1986. Chironomidae of the Hol- 281-291. DOI: https://doi.org/10.14430/arc- arctic region Part 2. Pupae. Entomologica tic4730 Scandinavica Supplement, 482p. Oliver, D.R., and Danks, H.V. 1972. Sex ratios of some high arctic Chironomidae (Diptera). - The Canadian Entomologist 104(9), 1413-1417.

Article submitted 3. March 2020, accepted by Torbjørn Ekrem 25. August 2020, published 13. September 2020.